Meteorologists predict that we may see an El Nino in 2014, which means that it might be a good time to brush up on what the heck this supposedly terrifying weather phenomenon actually is. Here's what you need to know. 

So what is an El Nino?

According to NOAA, El Nino "refers to the large-scale ocean-atmosphere climate interaction linked to a periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific." In other words, warmer water in the Pacific that messes up normal weather patterns across our continent.

An El Nino event typically occurs once every several years. The last El Nino we saw was in 2004, but the one before that, in 1997, is considered a textbook example of a strong El Nino. According to NASA climatologist Bill Patzert, "a pattern of sea surface heights and temperatures has formed that reminds me of the way the Pacific looked in the spring of 1997." Data collected by a NASA satellite shows a series of "Kelvin waves," or massive oceanic ripples that could suggest an upcoming El Nino. It will take a few months before we know whether or not we'll seen a El Nino this year. NASA offers some more information on how an El Nino is formed: 

Was the 1997 El Nino that bad?

In a word, yes. In Peru, the weather event caused massive amounts of rainfall which led to deadly flooding and mudslides and cost $2 billion in damage. The climactic changes created Hurricane Linda off the coast of Mexico, which turned into the strongest Eastern Pacific tropical cyclone ever recorded. Another hurricane hit Mexico a month later. The extreme weather spurred cycles of mosquito-transmitted diseases in Africa. Meanwhile, other countries experienced severe drought. In August of 2012, Nature published a report showing that El Nino events "suppress the monsoon rains that usually put a damper on the use of fire to clear land for agriculture." That means more pollution, which means more deaths — as many as 15,000 more in El Nino years, according to the report. 

In the U.S., the weather event didn't take quite as much of a toll. According to the Weather Underground, El Nino mostly just caused excessive rainfall in North America: 

In the U.S., the most significant manifestation of the El Niño were the record rainfalls in California during the water season of 1997-1998. Santa Barbara received 21.74” of precipitation in February alone contributing to its wettest water season on record (July 1-June 30) with a 46.99” total. Other California cities that reported their wettest season on record included Bakersfield (14.66”), Fort Bragg (79.13”), Monterey (47.12”), and Santa Maria (32.56”).

As a result of the environmental tumult, 1998 was one of the hottest years to date. 

What about the 2014 El Nino?

If we do see an El Nino event in 2014, it's not totally clear what that would mean for the U.S. The Midwest could see a cooler than usual—  or warmer than usual —summer depending on when the weather event hits, reports CBS Chicago:

According to the National Weather Service, the region has an “enhanced chance” for below normal temperatures from June through August. An El Nino episode is developing in the tropical Pacific, and this tends to favor cooler conditions in the summer here. Timing is the key: If El Nino conditions set up soon, then cooler temperatures are possible. However, if it arrives later there is an equal chance of warmer than average temperatures as well.

Summer weather aside, an El Nino this year could actually be a good thing for the U.S., per the Weather Underground

Researchers have found that instances of Atlantic tropical storms and hurricanes are usually reduced during an El Niño year. Based on the current model data, it appears that El Niño could develop near the height of the Atlantic hurricane season — potentially inhibiting some tropical development... If El Niño develops, beneficial rains could bring much-needed relief to some drought-stricken areas, most notably California. During El Niño, winters in parts of California are sometimes wetter than normal. But, before the beneficial rains arrive, Californians would likely have to endure a grueling drought through the spring and summer.

In other parts of the world, like Indonesia, an El Nino could mean an unwelcome dry spell. Beyond that, we'll have to wait and see.